Variable valve lift apparatus

ABSTRACT

A variable valve lift apparatus include a cam rotating together with a camshaft, a lever body being rolling-contacted to one end portion of the cam, and making a lever motion by receiving torque of the cam, two valves operating depending on a lever motion of the lever body, a valve gap control device being disposed at the other end portion of the lever body to simultaneously push the two valves by a main lift and controlling a gap of the valve, and an operation portion operated to selectively push a variable valve which is one among the two valves by a sub lift and disposed at the other end portion of the lever body.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No. 10-2016-0167758 filed on Dec. 9, 2016, the entire contents of which are incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a variable valve lift apparatus. More particularly, the present invention relates to a variable valve lift apparatus capable of varying the profile of a valve for improving efficiency of an engine.

Description of Related Art

Generally, an internal combustion engine receives fuel and air into a combustion chamber and generates power by combusting the fuel and the air. Herein, an intake valve is operated by the drive of a camshaft, and air flows into the combustion chamber while the intake valve is open. In addition, an exhaust valve is operated by the drive of a camshaft, and air is exhausted from the combustion chamber while the exhaust valve is open.

Meanwhile, optimal operations of the intake valve or the exhaust valve are determined according to the rotation speed of the engine. That is, lift and open and close timing of the valves are properly controlled according to the rotation speed of the engine. A variable valve lift (VVL) apparatus has been developed in which the valves are operated for various lifts according to a rotation speed of the engine for realizing optimal operations of the valves. For example, there is a variable valve lift apparatus wherein a plurality of cams for operating the valves by each different lift are provided to the camshaft, and the cam operating the valves is selected according to condition.

When the plurality of cams are provided to the camshaft, however, the configuration for selectively changing the cam to operate the intake valve or the exhaust valve may become complex, and interference between the elements of the configuration may occur. Meanwhile, in the case that the plurality of cams are respectively and independently operated for preventing the interference between the elements of the configuration, an additional constituent element is required at each cam for operating the cam wherein the cost may be increased.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a variable valve lift (VVL) apparatus having advantages of varying the profile of a valve according to the rotation of one cam using a simple configuration.

The variable valve lift apparatus according to an exemplary embodiment of the present invention may include a cam rotating together with a camshaft, a lever body being rolling-contacted to one end portion of the cam and making a lever motion by receiving torque of the cam, two valves configured to operate depending on a lever motion of the lever body, a valve gap control device disposed at the other end portion of the lever body configured to simultaneously push the two valves by a main lift and controlling a gap of the valve, and an operation portion configured to selectively push a variable valve which is one among the two valves by a sub lift and disposed at the other end portion of the lever body.

A roller may be disposed at a portion which the lever body is in contact with the cam.

The operation portion may include an actuator operated by hydraulic pressure, a chamber which is a volume selectively forming high pressure depending on an operation of the actuator, a plunger making a reciprocal rectilinear motion according to the pressure change of an internal of the chamber, and a solenoid valve operated to selectively supply hydraulic pressure to the actuator.

The plunger may selectively push the variable valve by the sub lift, and an elastic portion may be disposed at a lower end portion of the plunger which pushes the variable valve.

The sub lift of the variable valve may be a lift which is lower than the main lift.

An elastic portion may be disposed at a lower end portion of the valve gap control device which simultaneously pushes the two valves.

The variable valve lift apparatus may further include a valve bridge connecting the two valves.

The lower end portion of the valve gap control device may push the valve bridge.

The variable valve may be disposed to be vertically movable on the valve bridge.

The variable valve lift apparatus may further include a tappet disposed at an upper end portion of the variable valve on the valve bridge to realize a relative up and down motion of the variable valve.

The cam may include a base formed in an arc shape having a uniform radius and a circle center which is a rotation center of the cam, a sub lobe pushing the lever body from when the opening of the variable valve is started to when the closing of the variable valve is ended while the variable valve is operated by the sub lift, and a main lobe pushing the lever body from when the opening of the two valve is started to when the closing of the two valve is ended by the main lift.

An external diameter of the sub lobe may be larger than an external diameter of the base, and an external diameter of the main lobe may be larger than an external diameter of the sub lobe.

The base and the main lobe may be formed at opposite sides to each other with respect to a rotation center of the cam, and the sub lobe is formed between the base and the main lobe.

The sub lobes may be formed at both sides with respect to a rotation center of the cam.

When the operating portion is not operated, the variable valve may not be pushed by the operating portion even while the sub lobe of the cam is in contact with the lever body.

When the solenoid valve is to be ON wherein hydraulic pressure is supplied to the chamber by an operation of the actuator while the sub lobe of the cam is in contact with the lever body, the plunger may be moved downwardly, pushing the variable valve.

When the main lobe of the cam is in contact with to the lever body, the plunger may return to an original position thereof as the solenoid valve is to be OFF wherein hydraulic pressure is released from the chamber by stop of operating the actuator.

The variable valve may be operated by the sub lift during an intake stroke of an engine, realizing internal exhaust gas recirculation.

The variable valve may be operated by the sub lift during a compression stroke of an engine, realizing engine brake.

The time of opening an exhaust opening by the variable valve may be a top dead center.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a variable valve lift apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a drawing illustrating a shape of a cam according to an exemplary embodiment of the present invention.

FIG. 3, FIG. 4 and to FIG. 5 are operation diagrams of a variable valve lift apparatus according to an exemplary embodiment of the present invention.

FIG. 6 and FIG. 7 are graphs depicting valve profile depending on a variable valve lift apparatus according to an exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of a variable valve lift apparatus according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a variable valve lift apparatus according to an exemplary embodiment of the present invention includes a lever body 10, a lever rotation shaft 15, a cam contact portion 20, a cam 25, an operating portion 30, a solenoid valve 40, a valve gap control device 50, a valve 60, a valve bridge 70, and a tappet 80.

The lever body 10 makes a lever motion by receiving torque of a camshaft to operate the valve 60. In addition, the cam 25 is formed or disposed at the camshaft to transform a rotational motion of the camshaft to a lever motion of the lever body 10. Herein, the valve 60 may be an intake valve or an exhaust valve of an engine. According to an exemplary embodiment of the present invention, the valve 60 is applied as an exhaust valve, but it is not limited thereto.

The lever rotation shaft 15 is a shaft having a cylindrical shape as a rotation center of a lever motion of the lever body 10, and is rotatably connected to the lever body 10. In addition, the lever rotation shaft 15 is disposed in parallel with the camshaft to penetrate the lever body 10. Herein, disposition of the camshaft is well known to a person of ordinary skill in the art, so descriptions thereof will be omitted.

The cam contact portion 20 is formed or disposed at one end portion of the lever body 10. In addition, the cam contact portion 20 is rolling-contacted with the cam 25 to transform a rotational motion of the camshaft to a lever motion of the lever body 10. Further, the cam contact portion 20 may be a roller which is connected to the lever body 10 to rotate around a rotation shaft being parallel with the camshaft disposed or formed at the lever body 10.

The operating portion 30 is disposed at the other end portion of the lever body 10. In addition, the operating portion 30 includes an actuator 32, a chamber 34, a plunger 36, and a plunger elastic portion 38.

The actuator 32 is operated by hydraulic pressure. In addition, the actuator 32 is mounted to be inserted into the other end portion of the lever body 10.

The chamber 34 is a volume in which high pressure is selectively formed depending on the operation of the actuator 32.

The plunger 36 makes a reciprocal rectilinear motion depending on the change of pressure in the chamber 34. In addition, the plunger 36 may be disposed to be inserted into the other end portion of the lever body 10. Further, the chamber 34 may be disposed between the actuator 32 and the plunger 36.

The plunger elastic portion 38 is provided to the plunger 36. In addition, the plunger elastic portion 38 is disposed at an opposite side of the chamber 34 with respect to the plunger 36. In the present regard, the opposite side is a lower end portion of the chamber 34 which faces toward the valve 60. Meanwhile, the plunger elastic portion 38 may include a rubber material.

The solenoid valve 40 is operated to selectively supply hydraulic pressure to the actuator 32. In addition, the solenoid valve 40 is operated by a solenoid which is to be electrically switched On or off. The solenoid and the control thereof are well known to a person of ordinary skill in the art, so detailed descriptions thereof will be omitted.

The valve gap control device 50 is configured for controlling a gap of the valve 60. In addition, the valve gap control device 50 is disposed at the other end portion of the lever body 10 to be distanced further from the lever rotation shaft 15 in comparison with the operating portion 30. Further, a gap elastic portion 58 is disposed at a lower end portion of the valve gap control device 50 and faces towards the valve 60. Meanwhile, the gap elastic portion 58 may include a rubber material. Herein, the basic composition and function of the valve gap control device (lash adjuster) are well known to a person of ordinary skill in the art, so descriptions thereof will be omitted.

The valve 60 includes a variable valve 61 and a fixed valve 62, and the valve bridge 70 connects an upper end portion of the variable valve 61 with an upper end portion of the fixed valve 62. That is, an engine, to which the variable valve lift apparatus according to an exemplary embodiment of the present invention is applied, may be an two exhaust valve engine which is configured so that two exhaust valves perform exhaust in one cylinder.

The variable valve 61 is disposed to be movable up and down on the valve bridge 70 to be selectively operated by a sub lift depending on the operation of the operating portion 30. Herein, the sub lift may be a low lift wherein the variable valve 61 is operated to be independent with operation of the fixed valve 62.

The fixed valve 62 is fixed to the valve bridge 70 to be always operated by a main lift. Herein, the main lift may be a normal lift wherein the variable valve 61 is operated together with the fixed valve 62 by an equal lift while the fixed valve 62 is operated.

Meanwhile, the normal lift and the low lift are lifts of the valve 60 predetermined according to a design of a person of ordinary skill in the art, and lift duration of opening the valve 60 and lift width of the valve 60 by the low lift are shorter than that of the normal lift. However, lift for operating the variable valve 61 to be independent with to operation of the fixed valve 62 is not limited to the low lift, and may be changed depending on a design of a person of ordinary skill in the art.

The tappet 80 is disposed at the upper end portion of the variable valve 61, and is configured to realize an up and down motion of the variable valve 61 at the valve bridge 70. In addition, the tappet 80 is disposed to be inserted into a tappet hole 75 formed at the valve bridge 70 to penetrate to the valve bridge 70. Herein, the basic composition and function of the tappet as a valve device having a cylindrical shape are well known to a person of ordinary skill in the art, so detailed descriptions thereof will be omitted.

FIG. 2 is a drawing illustrating a shape of a cam according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the cam 25 according to an exemplary embodiment of the present invention includes a base 27, a sub lobe 28, and a main lobe 29.

The base 27 is a base circle of an external circumference of the cam 25 and is formed in an arc shape having uniform radius and a circle center C which is the rotation center (C).

The sub lobe 28 is a portion of an external circumference of the cam 25 configured for pushing the cam contact portion 20 from when the opening of the variable valve 61 occurs, which is selectively operated by a sub lift depending on an operation of the operating portion 30, is started to when the closing of the variable valve 61 has ended depending on rotation of the cam 25.

The main lobe 29 is a portion of an external circumference of the cam 25 configured for pushing the cam contact portion 20 from when the opening of the valve 60 is started to when the closing of the valve 60 has ended by a main lift depending on rotation of the cam 25. That is, an external diameter of the sub lobe 28 is larger than an external diameter of the base 27, and an external diameter of the main lobe 29 is larger than an external diameter of the sub lobe 28. In addition, the base 27 and the main lobe 29 are formed at opposite sides to each other with respect to a rotation center (C) of the cam 25, and the sub lobes 28 are formed at both sides with respect to a rotation center (C) of the cam 25 between the base 27 and the main lobe 29.

FIG. 3, GIG. 4 and to FIG. 5 are operation diagrams of a variable valve lift apparatus according to an exemplary embodiment of the present invention.

FIG. 3 illustrates a state of not operating the operating portion 30.

As shown in FIG. 3, when the operating portion 30 is not operated, the variable valve 61 is not operated by a sub lift even while the sub lobe 28 of the cam 25 is in contact with the cam contact portion 20. That is, when the operating portion 30 is not operated, a state that the plunger elastic portion 38 is separated from the tappet 80 is maintained even while the sub lobe 28 of the cam 25 is in contact with the cam contact portion 20.

FIG. 4 illustrates a state of operating the operating portion 30.

As shown in FIG. 4, when the operating portion 30 is operated, the variable valve 61 is operated by a sub lift while the sub lobe 28 of the cam 25 is in contact with the cam contact portion 20. That is, when the solenoid valve 40 is to be ON wherein hydraulic pressure is supplied to the chamber 34 by an operation of the actuator 32 while the sub lobe 28 of the cam 25 is in contact with the cam contact portion 20, the plunger 36 is moved downwardly wherein the plunger elastic portion 38 pushes an upper end portion of the tappet 80. In FIG. 4, a relative lift size (a) of the variable valve 61 from the fixed valve 62 having a state of a zero lift is illustrated by adjoint lines.

FIG. 5 illustrates a state of positioning the operating portion 30 to an original position thereof.

As shown in FIG. 5, when the main lobe 29 of the cam 25 is in contact with the cam contact portion 20, the plunger 36 returns to an original position thereof as the solenoid valve 40 is to be OFF wherein hydraulic pressure is released from the chamber 34 by stop of operating the actuator 32. At the present time, the gap elastic portion 58 of the valve gap control device 50 pushes the valve bridge 70, and the variable valve 61 and the fixed valve 62 are operated together by a main lift.

FIG. 6 and FIG. 7 are graphs depicting valve profile depending on a variable valve lift apparatus according to an exemplary embodiment of the present invention.

In FIG. 6 and FIG. 7, a lift profile of an intake valve (IL) is illustrated as a point chain line, and a main lift profile (EL) of the valve 60, which is described as an exhaust valve according to an exemplary embodiment of the present invention, is illustrated as a solid line, and a sub lift profile of the variable valve 61 among the valve 60 is illustrated as a dotted line.

As shown in FIG. 6, the variable valve 61 may be operated by a sub lift during an intake stroke of an engine after operating the variable valve 61 and the fixed valve 62 by a main lift. In the present case, a section S1 of operating the variable valve 61 by a sub lift is to be a section S1 of recirculating exhaust gas in an engine (internal exhaust gas recirculation section S1). That is, as the variable valve 61 opens an exhaust opening during an intake stroke, the Internal EGR, that exhaust gas exhausted through the exhaust opening is flowed into a combustion chamber by negative pressure of the combustion chamber, is realized.

As shown in FIG. 7, the variable valve 61 may be operated by a sub lift during a compression stroke of an engine before the main lift operation of the variable valve 61 and the fixed valve 62. In the present case, a sub lift operation section S2 of the variable valve 61 is to be an engine brake section S2. That is, as the variable valve 61 opens the exhaust opening during an intake stroke when braking, the engine brake can be realized by relieving compression of the combustion chamber. Meanwhile, the time that the variable valve 61 opens the exhaust opening during an intake stroke when braking may be a top dead center (TDC) of a piston.

According to an exemplary embodiment of the present invention, as one among two valves 60 which are simultaneously opened by a main lift is selectively opened by a sub lift, efficiency of an engine may be maximized. In addition, the internal exhaust gas recirculation and the engine brake can be achieved depending on the operation of the valve 61 which is selectively opened by a sub lift.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “internal”, “outer”, “up”, “down”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A variable valve lift apparatus comprising: a cam rotating together with a camshaft; a lever body being rolling-contacted to a first end portion of the cam, and making a lever motion by receiving torque of the cam; two valves operating depending on the lever motion of the lever body; a valve gap control device being disposed at a second end portion of the lever body to simultaneously push the two valves by a main lift and controlling a gap of the valves; and an operation portion operated to selectively push a variable valve which is one among the two valves by a sub lift and disposed at the second end portion of the lever body.
 2. The variable valve lift apparatus of claim 1, wherein a roller is disposed at a portion that the lever body is in contact with the cam.
 3. The variable valve lift apparatus of claim 1, wherein the operation portion includes: an actuator operated by hydraulic pressure; a chamber which is a volume selectively forming high pressure depending on an operation of the actuator; a plunger making a reciprocal rectilinear motion according to pressure change in an internal of the chamber; and a solenoid valve operated to selectively supply the hydraulic pressure to the actuator.
 4. The variable valve lift apparatus of claim 3, wherein the plunger selectively pushes the variable valve by the sub lift, and a plunger elastic portion is disposed at a lower end portion of the plunger.
 5. The variable valve lift apparatus of claim 1, wherein the sub lift of the variable valve is a lift which is lower than the main lift.
 6. The variable valve lift apparatus of claim 1, wherein a gap elastic portion is disposed at a lower end portion of the valve gap control device which simultaneously pushes the two valves.
 7. The variable valve lift apparatus of claim 6, further including: a valve bridge connecting the two valves, wherein the lower end portion of the valve gap control device is configured to push the valve bridge.
 8. The variable valve lift apparatus of claim 7, wherein the variable valve is disposed to be movable up and down on the valve bridge.
 9. The variable valve lift apparatus of claim 8, further including a tappet disposed at an upper end portion of the variable valve on the valve bridge to realize a relative up and down motion of the variable valve.
 10. The variable valve lift apparatus of claim 3, wherein the cam includes: a base formed in an arc shape having uniform radius and a circle center which is a rotation center of the cam; a sub lobe pushing the lever body from when opening of the variable valve is started to when closing of the variable valve is ended while the variable valve is operated by the sub lift; and a main lobe pushing the lever body from when opening of the two valve is started to when closing of the two valve is ended by the main lift.
 11. The variable valve lift apparatus of claim 10, wherein an external diameter of the sub lobe is larger than an external diameter of the base and an external diameter of the main lobe is larger than an external diameter of the sub lobe.
 12. The variable valve lift apparatus of claim 10, wherein the base and the main lobe are formed at opposite sides to each other with respect to a rotation center of the cam, and the sub lobe is formed between the base and the main lobe.
 13. The variable valve lift apparatus of claim 12, wherein the sub lobes are formed at a first side and a second side with respect to a rotation center of the cam.
 14. The variable valve lift apparatus of claim 10, wherein when the operating portion is not operated, the variable valve is not pushed by the operating portion even while the sub lobe of the cam is in contact with the lever body.
 15. The variable valve lift apparatus of claim 10, wherein when the solenoid valve is to be ON wherein hydraulic pressure is supplied to the chamber by an operation of the actuator while the sub lobe of the cam is in contact with the lever body, the plunger is configured to be moved downwardly, pushing the variable valve.
 16. The variable valve lift apparatus of claim 10, wherein when the main lobe of the cam is in contact with the lever body, the plunger returns to an original position thereof as the solenoid valve is to be OFF wherein hydraulic pressure is released from the chamber by stop of operating the actuator.
 17. The variable valve lift apparatus of claim 1, wherein the variable valve is configured to be operated by the sub lift during an intake stroke of an engine, realizing internal exhaust gas recirculation.
 18. The variable valve lift apparatus of claim 1, wherein the variable valve is configured to be operated by the sub lift during a compression stroke of an engine, realizing engine brake.
 19. The variable valve lift apparatus of claim 18, wherein a time of opening an exhaust opening by the variable valve is a top dead center. 